Thanks for reply,if we use columns or * will it make any performance difference? and also
Like ex : if exists(Select 1 ... ) or if exists(select Top 1 1 ....)
No and no
using a SELECT 1, avoids having to look at any of the meta-data that is not even needed to check the existancee of the records form the table?
Got nothing to do with metadata. EXISTS only cares about whether there is a row or not, it doesn't look at columns, it doesn't care.
Don't waste your time trying to do micro-optimisations. Silly tricks like this do not make major performance differences.
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
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